The present invention relates to data storage and, more particularly, to cartridge structures for housing data storage disks.
Data storage is an important aspect of today""s information technology. A great deal of effort has been made by the storage industry to increase the areal data density of a storage medium in order to meet the ever increasing demand for higher capacity storage devices.
Magnetic storage devices such as fixed or removable magnetic disks and tapes are widely-used conventional storage devices. The state-of-art conventional magnetic hard drive systems can achieve extremely high linear bit densities, especially with the new MR and GMR magnetic heads. For example, the areal density of many hard disk drives is on the order of magnitude of about one gigabit per square inch. One limitation in increasing areal data density in a magnetic device is the particle size or the characteristic dimension of a typical magnetic domain of the magnetic recording materials. Other limitations include the width of the magnetic read/write head and the limitations of mechanical tracking. Therefore, these hard drives are typically limited to less than 10,000 tracks per inch.
Optical storage devices are emerging as an alternative technology to the conventional magnetic technology because of their potential for high density data storage. In optical recording, data is represented as an optically readable domain on a recording medium such as an optical disk. Optically readable data can be recorded on a disk using a variety of mechanical or optical techniques. For example, CD disks typically are prerecorded using mechanical stamping and molding steps. So-called xe2x80x9crite-oncexe2x80x9d media, such as CD-R disks, can be recorded permanently with optical techniques to record particular data. As an alternative to permanent recording, magneto-optic and phase change disks allow data to be recorded in an xe2x80x9cerasablexe2x80x9d or xe2x80x9crewritablexe2x80x9d manner. DVD disks, for example, can provide prerecorded content or be configured for rewritable recording by an end user.
Optical storage disks and, in particular, magneto-optical disks offer greatly increased data storage capacity relative to other disk media, such as magnetic disks. The storage capacity for a given optical disk depends on the recording area of the disk and the areal density of domains recorded over the recording area. The recording area of a disk ordinarily is limited by physical requirements such as size and weight for minimal footprint and ease of portability. Accordingly, the pursuit of greater storage capacity has focused primarily on increased areal density over a given recording area. Optical recording offers relatively high areal density capabilities, but has been limited by the spot size of the optical beam used for read and write operations. In other words, areal density remains a function of the ability of the write and read beams to address increasingly smaller domains on the disk surface.
The areal density of an optical storage device, in principle, is only limited by the diffraction limit of an illuminating optical beam for reading or writing. One type of commercial optical storage technology is based on magneto-optical materials. These materials can currently produce an areal data density of about one gigabit per square inch. One well-known approach to increase the areal data density in an optical storage system is using smaller beam size. Due to the diffraction limit, this may be achieved by using a light source with shorter wavelengths such as those toward the blue end of the spectrum. For example, one application for the industrial development of compact blue lasers is aimed at the optical storage. Alternatively, one may increase the numerical aperture of the objective lens in the system to focus a beam at a given wavelength to a smaller spot within the diffraction limit.
The present invention is directed to a data storage disk cartridge having a dual housing structure, and to techniques for limiting the effects of debris in a data storage system. The disk cartridge includes an inner housing that contains the disk, and an outer housing that contains the inner housing. The inner housing is at least partially removable from the outer housing for insertion into a disk drive. The outer housing remains external to the disk drive, however, except for a portion that is inserted into the drive to provide a docking channel for removal of the inner housing. A shutter on the inner housing covers a portion of the disk, and is manipulable by the disk drive to uncover the disk and allow access by the drive head. The dual housing structure of the cartridge can significantly improve disk and drive reliability, especially for recording applications that require higher areal recording densities or reduced air gaps between the disk and the drive head. In particular, the disk cartridge reduces the accumulation of debris on the disk and drive components. The reduced amounts of debris contribute to more consistent performance of the disk and drive, and thereby enhance data storage reliability. For optical disks and drives, in particular, reduced amounts of debris are important for reliable optical and mechanical performance.
Debris is a significant concern in data recording systems. Debris can degrade the optical performance of an optical disk or the components of an optical drive. Debris that accumulates on the optical components of a drive, for example, can attenuate the intensity of the beams used for read or write operations. Consequently, the optical components can deliver a beam with insufficient energy, imprecise spot size, or misregistered addressing. Accumulation of debris on the disk can cause loss of tracking as well as attenuation of read and write beam energy. Debris can also cause disk tilt and, in some cases, drive head crashes. With substantial amounts of debris, disk or drive failure can occur, leading to data loss and repair costs.
The debris problem becomes more pronounced as areal density increases in an optical recording system. Optical disks with lower areal densities ordinarily tolerate some degree of optical error, and therefore are not as greatly impacted by debris. Also, to the extent that optical error is a concern, conventional recording drives typically make use of focus adjustment, interleaved data formats, and error correction. At higher areal densities, however, debris can impair the ability of the drive laser to consistently write and read to and from individual domains on the disk despite such measures. In other words, the more aggressive areal densities required by newer recording techniques may offer very little tolerance for optical error induced by debris. Accordingly, the absence of debris is a critical concern in high density optical recording applications.
An example of an optical recording application with extremely high areal density requirements is near field recording. Near field recording is one form of optical recording that is capable of producing extremely small spot sizes, for example, on magneto-optic disk media. For near field recording, a solid immersion lens (SIL) can be used to transmit an optical beam across an extremely thin air bearing, and through the top of the recording medium to the recording layer. The beam is xe2x80x9cair-incidentxe2x80x9d in the sense that it does not pass through the disk substrate before it reaches the recording layer. This aspect of near field recording differs from the substrate-incident techniques used in conventional magneto-optic recording, in which the beam passes through the substrate. A SIL can be integrated with a flying magnetic head assembly that hovers above the disk during operation and provides the magnetic bias for magneto-optic recording. For near-field recording, the thickness of the air gap is less than one wavelength of the recording beam. Transmission of the beam is accomplished by a phenomenon known as evanescent coupling, which results in extremely small spot sizes.
As an example, the near field recording technique is expected to offer storage in the range of 10 to 20 gigabytes (GB), and higher, e.g., for optical disks having diameters in the range of 120 to 130 millimeters (mm). Resulting domain sizes may approach, for example, 0.05 to 0.06 square microns per data domain. In dual-sided recording applications, the above figures pertain to each side of the disk. Near field recording, with increased areal density, is more susceptible to the performance problems caused by debris. Debris can affect not only optical performance, but also mechanical performance. With existing disk cartridges, debris can be carried into the drive on the surface of the cartridge. Also, debris can accumulate on the disk surface when the shutter is opened outside of the drive. As a result, debris in the form of dust, lint, or fingerprints can accumulate on the surface of the disk.
The debris problem can be aggravated by the physical characteristics of the near field recording process. Specifically, the beam is emitted across the extremely thin air bearing that separates the lens from the disk. The air gap is less than a single wavelength of the incident beam to take advantage of the phenomenon referred to as evanescent coupling. Variation in the air bearing thickness can result in varying focus and spot size across the disk. In particular, the thickness of the air gap determines the amount of radiation received by the recording layer via evanescent coupling. Significant variation in spot size and focus can undermine the ability of the laser to consistently address extremely small domains. Excessive amounts of debris on the disk can cause acute changes in air bearing thickness for successive domains and resultant loss of tracking. In extreme cases, head crashes, i.e., physical contact of the head with the disk, can result. In this manner, debris can compromise the mechanical performance of the near field recording system. Debris-induced head crashes are also a concern in other types of recording applications involving small air gaps between the disk and the drive head.
To alleviate the problems of debris in an optical recording system, and particularly in a near field recording system, the dual-housing disk cartridge of the present invention provides a system of partially redundant barriers that significantly reduce the possibility of debris accumulation. The barriers form a hierarchy of cleanliness, much like a clean room environment. The barriers isolate the disk and drive components from the outside environment. In one embodiment, the disk is never exposed to the outside environment. The inner housing in the cartridge provides a main line of defense against the accumulation of debris on the disk. The inner housing encloses the disk and includes a shutter that preferably is opened only by the disk drive. To that end, the inner housing may include a locking mechanism that is manipulable by the disk drive to obtain access to the disk. The shutter also can be spring biased in a closed position. In one embodiment, the shutter can be loaded by a spring that is selectively loaded in a ratcheted matter to preset a desired spring bias. Further, even if the shutter locking mechanism is somehow defeated, the disk cartridge includes the outer housing, which contains the inner housing. In this manner, the outer housing protects the exterior surface of the inner housing from debris.
The inner housing preferably is configured such that it can be removed only by the disk drive. In particular, it is desirable that the inner housing only be removable when the outer housing is partially inserted into the drive. The outer housing provides a docking channel for insertion of the inner housing into the drive. The major portion of the outer housing remains external to the drive, however, preventing introduction of debris from the outer housing into the drive. A second locking mechanism can be provided for general protection against removal of the inner housing from the outer housing. In addition, the outer housing can be equipped with doors that close off the inner housing absent engagement by the drive. With this combination of features in a preferred embodiment, the inner housing and the enclosed disk are never exposed to the environment outside of the drive.
In particular, in a preferred embodiment, the disk and inner housing are never touched by human hands. Instead, the outer housing acts as a special carrier for the disk and inner housing, and allows implementation of a docking station with the drive. In loading a disk, the carrier is temporarily docked to the drive. The carrier door is then opened and the cartridge is automatically removed from the carrier and transferred into the disk drive. In this embodiment, the empty carrier can be removed from the disk drive. In unloading a disk, an empty carrier is temporarily docked to the drive. The docking system automatically transfers the cartridge from the disk drive to the carrier. The cartridge enclosed in the carrier is then removed from the disk drive. The carrier door remains closed if the carrier is not docked to the disk drive. A disk cartridge in accordance with an embodiment of the present invention thereby provides an added measure against the collection of debris on the disk, and also prevents collection of debris on the exterior of the inner housing. As a result, the cartridge is much less likely to introduce debris into the drive, protecting the optical and flying head components of the drive against such debris.
A number of additional features and advantages that further contribute to debris prevention and, in some cases, durability and manufacturability, can be realized by a cartridge according to the present invention. For example, the inner housing can be constructed such that only the hub on which the disk is mounted is accessible by the disk drive to rotate the disk. In other words, in one embodiment, the drive accesses only the hub and not the inner diameter of the disk. Accordingly, the portions of the disk forming the inner diameter at which the hub is mounted preferably are not exposed to the environment outside of the inner housing. Instead, the disk drive engages the hub alone for rotation of the disk, e.g., by a magnetic clutch and spindle motor. As an alternative, the disk may be manufactured without a hub and rotated directly at a central position with a rotating mechanical chuck.
Further, containment of the inner housing within the outer housing serves to protect the hub from debris. Accumulation of debris on the surface of the hub can cause disk tilt, potentially harming optical and mechanical performance. Debris can reduce the coefficient of friction between the hub and spindle motor rotating the hub. Reduced friction can cause the hub to slip on the spindle, particularly during the rapid acceleration to operating speed. Debris on the hub can be centrifuged outward onto the disk surface during operation, leading to air gap variations across the surface of the disk. The air gap variations can result in diminished optical performance and head crashes.
In addition to providing protection against debris, an inner housing can contribute a mechanical damping effect that stabilizes the disk against vibrations, whether induced during rotation or caused externally. This effect is particularly advantageous for disks with substrates manufactured from less rigid materials such as plastic. In a preferred embodiment, the disk is permanently housed in the inner housing, even during rotation and drive head access. Although the shutter is opened to provide disk access, the remainder of the inner housing substantially encloses the disk, providing a tight shroud-like enclosure. The clearance between the disk and this enclosure provides a damping system that stabilizes the disk against vibration. Specifically, the inner housing provides air damping between the disk and the inner surfaces of the inner housing. The air tends to resist deflection, deformation, or movement of the disk during rotation, acting to dampen vibration. In this manner, the inner housing is capable of reducing vibration amplitude and associated disk movement to help maintain optical and mechanical performance in the recording system. This damping effect also can reduce the magnetic chucking force required to hold the disk onto the spindle. In particular, the air damping counteracts the tendency of the disk to fly away from the spindle motor, e.g., in response to shock loads. Also, the air damping is effective in reducing tilt of the disk surface.
The shutter and the portion of the inner housing adjacent the shutter can be formed from different materials that are selected to minimize the generation of debris due to abrasion during shutter movement. The inner housing and shutter materials, as well as the outer housing material, also can be selected for effective thermal matching to avoid undesirable degrees of differential deformation during use. Further, guide rails can be incorporated in the outer housing to facilitate retraction of the inner housing. The guide rails and inner housing, as well as the outer housing if desired, can be fabricated from different materials to minimize the generation of debris during retraction.
The shutter can be mounted for movement over the exterior of the inner housing, if desired, thereby enhancing the pinch strength of the housing, minimizing the introduction of debris into the interior of the inner housing, and facilitating shutter installation. The outer housing may include a structure that abuts with the disk drive upon insertion of the cartridge, thereby controlling the depth of insertion to minimize the passage of debris. In addition, the inner housing may incorporate a filter that captures any debris that may flow through the inner housing, and particularly the debris directed to the disk periphery by the centrifugal forces created during spin-up of the disk. Further, brush, vacuum, or other debris removal devices may be provided in the drive to remove debris from the leading portion of the cartridge upon insertion into the drive. Also, a bias mechanism can be provided in the inner housing to bias the hub against an opening in the inner housing through which the hub is accessed by a drive clutch and spindle motor. The biased hub thereby acts to substantially seal the hub opening against the introduction of debris into the inner housing. If desired, the bias mechanism can be constructed with a ratcheting structure that allows the bias load to be preset during manufacturing.
In one embodiment, the present invention provides a data storage disk cartridge, the cartridge comprising an inner housing configured to receive a disk; and an outer housing configured to receive the inner housing, and to allow at least partial removal of the inner housing from the outer housing.
In another embodiment, the present invention provides an optical data storage disk cartridge comprising an optical data storage disk, an inner housing containing the disk, an outer housing containing the inner housing, wherein the outer housing is configured to allow at least partial removal of the inner housing from the outer housing, an access area formed in the inner housing to allow access to the disk, a shutter mounted on the inner housing, the shutter being movable to cover and uncover the access area, and a hub mounted in the disk, wherein a portion of the hub is accessible through the inner housing for access by the disk drive, the hub being rotatable by the disk drive to rotate the disk.
In a further embodiment, the present invention provides a data storage disk cartridge comprising a housing configured to receive a disk, a shutter mounted on the housing, the shutter being rotatable to cover and uncover an access area adjacent the disk, thereby allowing a disk drive to access the disk, wherein the shutter is mounted to rotate over an exterior surface of the housing, and a hub mounted in a central area of the disk, wherein a portion of the hub is accessible through the inner housing for access by the disk drive, the hub being rotatable by the disk drive to rotate the disk.
In an added embodiment, the present invention provides a housing for a data storage disk comprising a first major surface, a second major surface, first, second, and third side surfaces extending between the first and second major surfaces, and a slot formed opposite one of the side surfaces for receiving a second housing containing a data storage disk, wherein the. first major surface includes a major portion, a nose portion, and a transition portion defining an interface between the major portion and the nose portion, wherein the major portion and nose portion are sized such that at least the transition region defines a surface that is abuttable with a surface on the disk drive upon insertion of the nose portion into the disk drive, thereby limiting insertion of the housing.
In another embodiment, the present invention a data storage disk cartridge, the cartridge comprising an inner housing including an area to receive a disk and defining an access area, wherein the inner housing includes an identification area configured to carry a visual identification, a shutter that covers the access area, the shutter being movable to uncover the access area to allow access to the disk, an outer housing including an area to receive the inner housing, wherein the outer housing is configured to allow at least partial removal of the inner housing from the outer housing to allow the disk to be accessed by a disk drive, and wherein at least a portion of the outer housing is sufficiently transparent to allow visibility of the identification area of the inner housing from outside the outer housing.
In a further embodiment, the present invention provides a near field recording system comprising a cartridge including an optical data storage disk, an inner housing containing the disk, a shutter that is movable to allow access to the disk, and an outer housing containing the inner housing, wherein the inner housing is at least partially removable from the outer housing, and a disk drive including a mechanism that moves the inner housing relative to the outer housing and moving the shutter to access the disk, and a near field recording head assembly having a solid immersion lens that transmits a beam of radiation to record data on the disk via evanescent coupling.
In an additional embodiment, the present invention provides a method for protecting a disk from debris comprising housing the disk in an inner housing, housing the inner housing in an outer housing, and allowing removal of the inner housing from the outer housing only upon insertion of a portion of the outer housing into a data storage drive.
In a further embodiment, the present invention provides a method for protecting a data storage disk drive from debris, the method comprising housing a disk in an inner housing, housing the inner housing in an outer housing, and accessing the disk such that the inner housing is generally unexposed to any environment outside of either the outer housing or the disk drive.
In another embodiment, the present invention provides a data storage disk cartridge comprising a disk, and a housing structure having a plurality of enclosures arranged such that the disk is generally unexposed to any environment outside of either the housing structure or a disk drive.
In an added embodiment, the present invention provides an optical data storage disk cartridge comprising a optical disk, an inner housing containing the optical disk, an outer housing containing the inner housing, wherein the outer housing defines a slot for at least partial removal of the inner housing from the outer housing, a rotary shutter mounted over an exterior surface of the inner housing, the shutter being rotatable to cover and uncover the optical disk for access by a data storage drive, and a structure formed on the inner housing for engagement with an element in a disk drive to thereby allow at least partial removal of the inner housing from the outer housing.
In a further embodiment, the present invention provides a bias mechanism for a rotary shutter for a data storage disk cartridge, the rotary shutter having at least one mounting structure rotatably mounted to the disk cartridge, the bias mechanism comprising a spring having a first end, a first spring tail at the first end, and a second spring tail at the second end, a first pair of mounting posts coupled to rotate with the mounting structure of the shutter, each of the first pair of mounting posts engaging the spring at the first end on opposite sides of the first spring tail, and a second pair of mounting posts fixed to the cartridge, each of the mounting posts engaging the spring at the second end on opposite sides of the second spring tail, wherein the spring is rotationally loaded such that the second spring tail bears against at least one of the first pair of mounting posts and such that the first spring tail bears against at least one of the second pair of mounting posts, the spring thereby exerting a spring bias against the first mounting posts and against the shutter to bias the shutter toward a closed position.